An electron spin resonance investigation of the reactions in irradiated aqueous solutions of hydrogen cyanide and the cyanide ion

Use of the in situ radiolysis-esr method has shown that the reactions of H and OH with HCN in acid solutions yield the radicals H₂C=N (a^H = 87.2, a^N = 10.2 G, g = 2.0028) and HC(OH)=N (a^H = 54.40, a_OH^H = 0.89, a^N = 10.14 G, g = 2.00322), respectively. The pK for the dissociation of the OH proton in the latter radical is estimated to be ∼5. Scavenging of e_aq^- with HCN also yields H₂C=N. The reaction of OH and O- with CN- in alkaline solutions was found to produce the radical ·CONH₂ as observed either directly at pH ∼10 or by radical trapping with CH₂=NO₂^- at higher pH. Exactly parallel behavior was found for CN^- and HCONH₂ in basic solutions. However, HCONH₂ yielded only ·CONH₂ in acid and neutral solutions and no rearrangement of this radical to HC(OH)=N was found. The adduct to CH₂==NO₂- found in CN^- solutions and previously identified as NCCH₂NO₂- must now be assigned the structure H₂NCOCH₂NO₂-.